TEMPERATURE AND SALINITY TOLERANCE OF VIETNAMESE BAIT WORMS, NAMALYCASTIS SP.: IMPLICATIONS FOR ESTA

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TEMPERATURE AND SALINITY TOLERANCE OF VIETNAMESE
BAIT WORMS, NAMALYCASTIS SP. IMPLICATIONS FOR
ESTABLISHMENT OF A TROPICAL IMPORT IN THE
SOUTHEASTERN USA

• D.C. Miller, R.K. Dale and J.R. Brown
• University of Delaware, Lewes, DE, USA
•  dmiller_at_udel.edu, ryandale_at_udel.edu, jrbrown_at_ude
  l.edu
• P.D. Huggins
• Fairmont State College, Fairmont, WV, USA
• phuggins_at_mail.fscwv.edu

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Talk Outline

• What is Namalycastis sp?
• What is its invasion potential?
• Temperature and salinityexperiments
• Reproduction, regeneration, survivorship
• Ongoing cold acclimation experiment
• Tentative conclusion limited by 10 ºC isotherm
• Potential survival south of Charleston, SC

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Namalycastis sp.

• Undescribed species
• Family Nereididae
• subfamily Namanereidinae
• cf. Namalycastis abiuma
• Bright pink and gt2 m in length
• Mangrove swamps, dug from roots, Mekong Delta
• Vietnam ? Bay Area ? Mid-Atlantic

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Nuclear Blood Worms

• Sold as bait
• alternative to bloodworms
• do not bite or bleed
• 6 - 7 per container
• 2 - 3 worm per container, ? 50 g live weight

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Known Risks

• Media local and national print, plus local TV in
  2002
• Pathogens in soil packing material
• Including Vibrio cholera
• Now packed in newspaper compost
• No federal or state restriction on import and
  distribution
• Falls between established regulations and
  agencies
• Release through use as bait
• Cut bait or whole worms when discarded
• Long-term survival thought unlikely due to
  seasonally cold temperatures

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Potential Invader?

• Conventional wisdom is that there is little risk
  locally
• Worms die if refrigerated, kept for sale on
  counters at room temperature
• Could be sold as bait anywhere in US
• Cut bait, discarded whole animals
• Could be bought here and easily transported and
  released in southeast US
• I-95 corridor south to SE or Gulf coasts
• Seasonal temperature range likely would not
  necessarily prevent survival or establishment in
  southeast US

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Almost No Natural History Information

• Undescribed species in poorly known subfamily of
  clam worms
• Temperature and salinity tolerances poorly known
• Reportedly established in Hawaii
• In culture in France?
• Suitably warm, vegetated habitats certainly exist
  in US southeast in marshes and mangroves

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Goal

• To determine temperature and salinity tolerances,
  which combined with seasonal water temperature
  data, will permit science-based assessment of the
  risk of establishment of this species in Delaware
  and points south along the US east coast

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Temperature and salinity tolerance experiments

• Worms collected at Wal-Mart
• Lab bins with mud and salt marsh detritus
• Variations in moisture, salinity, sediment type
  and food supplements
• Temperature 22 25 ºC , salinity kept at 10 13
  ppt

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Temperature Setup

• Two replicate tanks, n10 worms each, 3 temps at
  once
• 11, 12 15, 16,25 ºC for 5 days
• Pretests and repeated twice with same results

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Temperature Results

• Fine at gt15 ºC for 5 days
• Quick death at 11 ºC
• Ho Chi Minh City
• 22 34 ºC year-round
• wet season May Nov
• dry season Jan - Mar

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Salinity Setup and Results

• Buckets in temperature control bath, 29 ºC
• N 10 worms at S 0, 25, 35 ppt
• Survive 0 to gt 30 salinity for almost 5 days

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Osmoregulation Capabilities

• 4 worms each at
• 0, 10, 20, 30 ppt
• No weight change at 10 ppt
• Gain at 0 ppt, lose at 20, 30 ppt
• Osmoconformers

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Other Observations

• Mortality 1 to lt 0.5 per day in culture
• Deposit feeder and scavenger, but have not
  observed predation
• Spontaneous fragmentationnear death
• Regeneration?

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Problems with Tropical Imports

• Diverse fauna, undescribed species
• Bait, exotic pets, novelty and cachet
• Collected at minimal cost by hand, with methods
  that may be environmentally damaging
• No regulation of harvesting in country of origin
• Extended collecting season, even year-round
• Shipped without need for refrigeration
• Lacking justification
• harmful effects not demonstrated, so why restrict?

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Some Biological Data Goes a Long Way

• Local culture would eliminate some, but not all
  problems
• Allow sale and use where deemed safe, but
  restrict or raise flags where survival cannot be
  excluded?
• NODC Coastal Water Temperature Guide or other
  real-time data products

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Next Steps

• Cold acclimation experiment completed no
  temperature acclimation observed
• Photoperiod?
• Wet-dry seasonality?
• Reproduction?
• Prey on local species?
• Temperature microclimates and microhabitats in
  local marshes and mangroves to south
• Support from the Sea Grant Aquatic Nuisance
  Species program

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Summary

• Habitatcryptic, in vegetation, semi-marine,
  semi-aquatic, semi-terrestrial
• Euryhaline and estuarine-tolerantsalinity not
  limiting
• Doubtful overwintering in Mid Atlantic
• lt10 ºC for 4-5 months each year average
• 10 ºC (or greater) is minimum temperature from
  about Charleston southward
• Cannot exclude possibility of invasion from there
  southward